1. Field of the Invention
The invention lies in the general field of noninvasive, ambulatory blood pressure measurement equipment. More specifically, the invention relates to an ambulatory, long term blood pressure monitoring system, where essentially all of the equipment components are mounted on the arm band that is conventionally used in existing blood pressure detecting systems.
2. Description of the Prior Art
Various methods have been utilized in the past for accurate blood pressure determination with the most common being a "tourniquet" type arm band with overlapping Velcro attachments applied around the biceps/triceps muscle area of the arm. The band would typically be constructed with an inflatable air bladder therein with a hand operated rubber bulb pump distally connected thereto via a lengthy air hose. The band would be initially tightened by increasing air pressure to a predetermined level to completely stop the flow of blood through the arm. Using the auscultatory method to listen for Karotcoff (K) sounds (bubbling blood squeezing through a compressed artery), a microphone or stethoscope would be applied to the arm over the brachial artery, immediately adjacent the arm band. The air pressure in the arm band would then be slowly released by a hand operated air release valve until the first K sound, the systolic, would be heard, i.e. the sound of blood initially bubbling through the artery. The fourth or fifth K sound, the diastolic, would follow in time as the arm band pressure is further released and as the blood, no longer constricted from flow, freely flows though the artery without bubbling. By such means, the systolic/diastolic blood pressure, typically being 120/80, and variations thereof, as well as the pulse rate, typically 60 beats/minute, could conveniently be determined.
More recent methods of implementing the foregoing blood pressure measurement have been devised to operate in a long term ambulatory environment by using a similar inflatable arm band with a lengthy air hose and electrical lead extending therefrom and attached to a magnetic tape recorder, usually mounted on a waist belt of the patient. A relatively large recorder enclosure/housing, containing not only the blood pressure data recording medium, i.e. magnetic tape reels, but also carried a pneumatic (air) pump and motor to inflate the air bladder, along with a printed circuit board for a microprocessor and appropriate electronics to accurately record periodic blood pressure events or specific event prompted blood pressure samples, and Liquid Crystal Display (LCD) screen with necessary control buttons (keyboard) for event marking or system control. A microphone would be attached by tape to the patient's arm under the inflatable arm band, with a lengthy electronic lead to the recorder housing to provide periodic blood pressure events to be recorded for later evaluation.
Several such prior art devices, elements and systems are illustrated in the following U.S. Pat. No. 5,485,848 (Jackson) describes a continuous blood pressure monitoring device mounted in a wrist watch fashion to detect systolic and diastolic pressure readings taken at the wearer's wrist and calibrates said readings in relation to a conventional upper arm cuff mounted sphygmomanometer device coupled by a conventional lengthy air tube to an air pump and appropriate electronics, central processor unit (CPU) and a stored calibration table. Such wrist mounted blood pressure sensing devices are not, however, usually taken at the same level as the heart of the patient which tends to yield inaccurate pressure variations, and furthermore, blood flowing through smaller arteries on the wrist do not yield the strong signature that can be found in the large brachial artery of the upper arm. Another U.S. Pat. No. 5,447,160 (Kankkunen) discloses a method for restricting the air pressure in the conventional upper arm cuff. Another prior art disclosure in U.S. Pat. No. 5 5,141,341 (Marangoni) discloses an ambulatory blood pressure device wherein the air pump, inflating valve and pressure transducer are all located in the arm mounted cuff. In yet another U.S. Pat. No. 5,351,694 (Davis), an adjustable, non inflatable arm band/cuff is applied to a limb to pick up blood pressure measurements and send the accumulated information by electrical lead, wireless, and optical transmission means for further analysis. U.S. Pat. No. 4,353,374 (Rebbe) disclosed a unique blood pressure band having a weighted buckle attached to an end of the band through which the other band end is passed through, forming a loop that tightens the band to an arm. Magnetic or other similar attaching means holds the band and loop in position. U.S. Pat. No. 5,218,966 (Yamasawa) teaches application of a photo electric sensor in a finger band to detect blood pressure. Yet another U.S. Pat. No. 5,121,954 (Holtsch) relates to a unique connecting means for forming an arm band, wherein a pin with inclined surfaces applied to a pair of transverse grooves is utilized to lock an arm band in position. U.S. Pat. No. 1,107,848 (Oku), discloses a non mobile blood pressure device wherein a cylindrical collar situated in a casing serves as an arm band and is adjusted by a sliding member coupled to a spring mounted knob. In U.S. Pat. No. 4,966,155 (Jackson), a waist mounted physiological monitor incorporates an electroconductive elastomeric means the resistance value of which changes as a function of the elongation of the elastic belt. U.S. Pat. No. 4,890,625 discloses a blood pressure cuff having an internal acoustic pickup coupled via a lengthy pneumatic tube to a first and second enclosures for converting acoustic signals to electrical signals.
The invention disclosed herein improves on the foregoing prior art blood pressure apparatus by encompassing a fully self contained blood pressure package on the cuff of the blood pressure inflatable arm band, and by such means, substantially shortening the air tube between air pump and air bladder, which in turn, dramatically increases system efficiency and decreases energy consumption, i.e. battery power. The lengthy tube of prior art pumps tended to waste battery power to run the electric motor of the air pump because much more pressure was required to pump a lengthy compressible volume of air along the lengthy air tube from the pump in the recorder mounted on the patient's waist up to the arm band to inflate the air bladder. The invention disclosed herein mounts the air pump, electric motor and all electronic components "on the arm band"; as a result, there is no lengthy pneumatic (air) hose and related volume of air to compress; therefor, there is no waste of energy in compressing air as with prior art. Additional problems are also eliminated by eliminating the lengthy air hose. There is frequently problems with the a "kinked" air hose especially during periods of sleep as the patient wearing the monitor roles over in bed; such a kinked/blocked off air hose invariably leads to inaccurate if not completely erroneous readings.
In addition, the invention herein further improves on the prior art by using the oscillatory method of blood pressure measurement; i.e. detecting variable air pressure changes or "pressure blips" to indicate the respective systolic/diastolic pressure measurements. The variable pressure measurement is made by an oscillametric sensor also mounted "in the arm band"; i.e. there is no longer any need to tape a microphone to the patient's arm as with existing art.
The invention herein further improves on the prior art in that, because the data recording means, also mounted in the arm band cincture housing, isn't the bulky and mechanically complex magnetic tape reels of prior art, but is instead a very compact and highly reliable digital integrated circuit technology (EEPROM) and the system display and control mechanism may now be confined to a very small housing that can conveniently be mounted in a device similar to a wrist watch or in a flip top module positioned on the arm band cincture housing instead of being mounted on a patient belt. The substantially smaller data recorder housing not only provides increased reliability but also much greater patient flexibility in mounting and accessing the recorder device.
The invention improves on the prior art in yet another manner in that the cincture housing for enclosure of all the ambulatory blood pressure detector equipment effects a much more convenient arm band mechanism that can be mounted by the patient alone with only one hand. The inconvenient Velcro attachment means of existing blood pressure systems often encounters difficulty in adjusting the arm band to varying sized patient arms in different surroundings, and requires at least two hands to mount. In addition, presently used Velcro type arm bands tend to incur slippage which in turn creates noise leading to numerous false readings.
Applicant's invention overcomes all the foregoing limitations of the prior art a solves a long standing need for a non obtrusive, non visual, non invasive, compact, hidden, and reliable ambulatory blood pressure recorder.